I found out how to get these four:
Frigisaurus: Go to the BB Base (after finishing the main plot) and get to the 6th floor. You'll find the BB trio Vivian, Snivels, and Rex. Agree to battle all 3 of them in a row. When you beat all 3 of them, you'll get Frigisaurus. You get Ignosaurus by defeating Saurhead after you beat the game.
Guhvorn, Guhweep, and Guhlith (Guhnash's brains). After you beat the main storyline, go to the warehouse in the Fossil Center. You'll see a new machine that looks like the teleporter, except it's blue instead of red. Talk to Dr. Diggins, and he'll tell you that he needs 3 more things to finish the time machine (which is what the blue thing is).
You'll need to battle somone to get each of the parts: Nevada (she's in the last room of the Digadigamid), Capt. Woolbeard (in the last room of the sunken ship, as always), and King Dynal (he's in the last room of the Dinurian spaceship... you'll need to use the teleporter to get to him). Once you beat all 3 of them, talk to Dr. Diggins again. He'll finish the time machine, and then let you use it as much as you want. When you use it, you'll be standing on the teleporter and asked whether you want to bring Duna or Rosie with you to battle Guhnash. Pick one, beat Guhnash, and you'll get Guhnash's brains to use in fossil battles!
Chat with our AI personalities
A place where you can store your fossils. You can store up to 100. It is good because since you can only have one of each vivosaur, move a dino medal into the bank and if you revive that head fossil again, you will receive a second kind of that vivosaur. Sort of like cloning.
you put vivos in the bank then find the heads again
You can find the sandal fossil for Nick Nack in Greenhorn Plains. Go there and then go to the very back and enter the place where the dino medals were stolen in the beginning of the game. You will meet Duna there and she will give you the fossil. Go back to the hotel and talk to Nick Nack again.
walk out and in again and ta-da! you have a Pokemon extracktid from a fossil
well you see it was very simple for me to get all 14 legendary vivosaurs 1. Frigi-saurus-- beat BB bandit trio post-game 2. Igno-saurus-- beat saurhead in the fossil stadium commons room 3. the gunhash brain trio-- go back in time* and fight gunhash again 4. Dynal, raptin, dinaurian robot dino, and duna-- revive 100 vivosaurs and fight dynal 5. chicken-- go on Nintendo channel on wii and prss the button that looks like two squares over lapsing scroll down to fossil fighters and go on dsi download play and wham fossils in fossil lawn